Microfluidic systems frequently necessitate actuators in the form of pumps and/or valves which control the transport of liquids through channels or channel systems. Such actuators may exemplarily be embodied such that a gas which acts directly or indirectly on a fluid in a channel or channel system is generated in a liquid (such as, for example, water) via an electrochemical reaction. Such an actuator liquid may exemplarily be an electrolyte wherein electrolysis is performed so as to achieve the actuator effect. When the electrolyte is a water-based electrolyte, hydrogen and oxygen gas, the gas pressure of which imparts an actuator effect, may exemplarily be generated by means of water electrolysis.
One problem here is that the liquid wherein a gas is to be generated electrochemically is present in the system in very small quantities and may evaporate quickly, thereby limiting the storability of the systems.
It is irrelevant for evaporation and, thus, the present invention whether the electrolyte is really present in a liquid state or is modified (such as, e.g., concentrated as a gel, etc.) in its state.
At the same time, the advantage of such an electrochemical actuator, i.e. displacing relatively large volumes by the great gas volume, is to be maintained. This means that the liquid in the actuator may not be sealed using a very thick or dense film. On the other hand, polymer films of low water vapor permeability, as are, for example, frequently used for drug packs, exhibit very high yield stress and only very low expandability.
When using an electrolyte containing water for the electrochemical actuator, water vapor permeability has to be very low, whereas the advantage of the great gas volume generated is to be maintained to the best degree possible. Conventional materials, like, for example, nearly all elastomers (which basically allow high expandability), but also most other plastic films, however, exhibit high permeability relative to water vapor. Technically, metallizations on or in these materials are also used frequently so as to reduce water vapor permeability. However, with the large expansion capabilities necessitated for the films at the same time, such a metallization would result in tears such that a stable barrier function could not be ensured. Thus, the invention aims at encapsulating an electrolyte, which generally contains water, such that the advantages of the great gas volume generated, compared to the actuator volume at normal pressure, can be maintained to the best degree possible, but at least are not reduced to such a degree that the actuator function can no longer be ensured.